Weighing scale



y 8, 1952 L. SuWlLLlAMS 2,602,659

WEIGHING SCALE Filed June 11, 1946 3 Sheets-Sheet l mmvron Lawrence S.MY/iam;

ATTORNEYS July Filed June 11, 1946 L. S. WILLIAMS WEIGHING SCALE 7 3Sheets-Sheet 2 INVENTOR.

ii I

Lawrence [MY/farms ORNEYS J y 8, 1952 s. WILLIAMS I 2,502,659

I WEIGI-IING SCALE Fiied June 11, 1946 s Sheets-Sheet s INVENTOR.Lawrence J. MOW/0x715 WMAZZZM' ATTORNEYS dition of level of the scale.when an intermediate lever system is interposed Patented July 8, 1952WEIGHING SCALE Lawrence S. Williams, Toledo, Ohio, assignor to ToledoScale Company, Toledo, Ohio, a corporation of New Jersey ApplicationJune 11, 1946, Serial No. 676,004 Claims. (01.265-61) This inventionrelates to weighing scales, and in particular to a weighing scale thatis constructed so that its indications of loadare not affected by anout-of-level condition of the scale.

Many weighing scales, including those employing automaticcounterbalancing and indicating mechanisms, are provided with wheels sothat they may be easily moved from one location to another. When thesescales are moved fromv place to place, they are used without beingprecisely level and itis desirable that their indica tions be correctregardless of their condition of level. When pendulums are used as loadcountcrbalancing elements in portable scales it is customary to use twosubstantially identical pendulums rotating in opposite directions sothat the indication, which is determined by the average of thecounterbalancing effects of the two pendulums, shall be unaffected bychanges in the con- It has been found between a load receiver leversystem and a double pendulum counterbalance, that the indications of thescale are still affected by changes in the condition of level of thescale. This tipping error is reduced when the indicator stands at zeroby shifting the center of gravity of one of the levers, usually thelever to which the tare beam is attached, in a vertical direction. Thusa portable weighing scale having a double pendulum counterbalance and atare beam lever whose centerof gravity may be moved vertically, may beadjusted to indicate correctly throughout its weighing range when thescale is level and to maintain correct Zero load indication as the scaleis tipped. However, errors in load indication still appear when thescale is tipped.

The principal object of this invention is to provide a portable weighingscale whose load indications are not affected by an out-of-levelcondition of the scale.

Another object of the invention is to provide a force transmitting leversystem that does not contribute any error to the indication of load whena weighing scale employing the lever sys- 1 tem is tipped.

Another object of the invention is to provide means for adjusting theunbalanced moments of each of several force'transmitting levers of aforce transmitting lever system.

These and other objects and advantages are apparent from the followingdescription, in which reference is made to accompanying drawings.

According to the invention the load indications of a portable weighingscale may be made immune to the scale being out-of-level if theresultant of the centers of gravity of the masses constituting theunbalanced weights of the levers moves along a line parallel to thenormally vertical center line of the scale. If the levers are fulcrumedon opposite sides of their common connection and are properlyproportioned, the change in pull of one lever produced by tipping thescale is counteracted by a corresponding change in pull of anotherlever, and the indication of the scale is not aifected.

An. example of a portable weighing scale constructed according to theinvention is illustrated in the accompanying drawings.

In the drawings:

Figure I is a front elevation of a portable weighing scale embodying theinvention.

Figure II is an enlarged fragmentary portion of the force transmittinglever system of the portable weighing scale.

Figure III is a plan view of one of the levers of the scale.

Figure IV is a plan view partly in section of the other lever of theforce transmitting lever system.

Figure V is a diagram of the lever system illustrating the levers intheir zero position.

Figure VI is a diagram of the lever system with the levers in their fullload position.

Figure VII is a fragmentary elevation of a lever. system showing anothermethod of providing initial pull without introducing an error when thescale is placed in an out-of-level condition.

As commonly constructed, a portable weighing scale includes a rigid baseI that is mounted on wheels 2 so that it may be readily moved from placeto place. A load receiver or platform 3, substantially coextensive inarea with the base I, is supported immediately above the base I' by alever system contained within the base. The lever system terminates in anose iron 4 that is located beneath a portion of the base I that is notcovered by the load receiver 3. The nose iron d is pivotally connectedto a steelyard rod '5 that extends upwardly through a hollow column 6erected on the base I. The upper end of the column 6 is expandedlaterally to provide a housing I for a tare beam lever 8 whose endsprotrude from the sides of the housing I; The upper end of the steelyardrod 5 is suspendedfr'om a stirrup 9 (Figure II) containing v-bearings itthat rest on a load pivot l l of the tare beam lever 8. The tare beamlever 8 is supported on a fulcrum pivot 12 that rests on V-bearings itof a fulcrum bracket l4 mounted in the housing portion '1 of the column5.

Forces are transmitted from the tare beam lever 3 through its powerpivot i5 that engages a V-bearing it mounted in the lower end of aconnection I? suspended from a load pivot l8 of a pendulum lever to.

The pendulum lever is is iulcrumed in a bracket 26 which is mountedwithin the rim of a substantially watchcase-shaped housing 2! (Figure I)surmounting the housing portion 1 of the column 6. The pendulum leverii] is connected through its power pivot 22 and astirrup, bearing andsteelyard rod assembly to a yoke 24 that is suspended from power ribbons25 of a pair of load oounterbalancing pendulums 2E. The loadcounterbalancing pendulums 25 are suspended on ribbons 27 that areattached to the upper end of a sector guide 22$ mounted verticallywithin the watchcase-shaped housing 2!. The power ribbons 25 and thesuspending ribbons 27 overlie power sectors 25} and fulcrum sectors 3%]respectively of the pendulums 28,

which sectors are proportioned so that the pendulums rotate outwardlyand roll upwardly along the sector guide 23 through distances that areproportional to the load forces that are being counterbalanced. Each ofthe pendulums 26 has a stem 3| on which a weight 32 is mounted. Theweight 32serves to determine the load counterbalancing capacity of thependulum and its position with respect to the sectors is adjustable inboth distance and angle to secure correct operation of the pendulum. Theturning centers of the pendulums 28 are interconnected by compensatingbars 33, from Whose midpoint is suspended a rack 34 that meshes with apinion on an indicator shaft to drive an indicator '35 through an anglethat is proportional to the load or force being counterbalanced. Theindicator cooperates with indicia 36 arranged on a chart 3! to indicatethe magnitude of the load.

The motion of the moving parts of the counterbalancing mechanism iscontrolled during changes in .load. by a hydraulic, dashpot 38 (FigureII) whose plunger actuating rod 39 is pivotally connected to the tarebeam lever t.

Since the accuracy of the load counterbalancing mechanism including thependulums 26 may be affected by accumulations of dust or other foreignmaterial, the watchcase-shaped housing .2! is sealed against theentrance of dust. To prevent the entrance of dust through the openingprovided for the interlever connection H, a liquid seal 30 comprising anannular cup 4! mounted in the housing 2! and an inverted cup 52 mountedon the connection l! and dipping into the liquid in the annular cup d!is provided.

The ends of the tare beam lever 8 that protrude through the sides of thehousing portion 1 of the column 6, carry forwardly extending brackets 43and 44 to which a pair of beams 45 and 45 are attached. The upper ofthese beams, the beam 45, is provided with a tare poise 4'! that may bepositioned along the beam 45 to offset the weight of a container orinitial load placed on the load receiver 3. The lower beam, the beam 46,carries a poise 48 that may be used to ofiset part of the load on theload receiver 3 and thereby increase the weighing capacity of the scale.The bracket 44 positioned at the fulcrum end of the tare beam lever 8has a cup-like cylindrical portion 49 extending longitudinally of thelever, the outer surface of which serves to pilot a telescoping cup-likecover 55. A laterally extending arm 5| of a tare beam loading box 52 isalso piloted on the cylindrical extension 49 and is clamped between thesurface of the bracket 44 and the rim'of the cup-like cover '50. A stud53 set in the bracket 44 outside of the cylindrical extension 49 andparallel thereto, prevents rotation of the cup-like cover 50 and alsoprovides means by which the position of the loading box with respect tothe lever may be secured. A balancing weight 54 carried on a threadedscrew 55 is positioned Within the cup-like extension 49 and isadjustable longitudinally of the lever by rotation of the screw 55. Apair of bolts 56 that pass through holes in the bottom of the cup-likecover 50 pass through slots in the sides of the balance weight 54 andare threaded into the bracket 44 to hold the assembly'together and toprevent the balance weight 54 from turning when the screw 55 is rotated.

The pendulum lever l9 (Figure 111) is provided with a cup-like loadingbox 5! on its end adjacent its power pivot 22. The loading box 51 servesas a receptacle for loading material 58 which serves to increase theforce with'whlch the pendulum lever pulls against'the pendulums.

In the example illustrated the upward pull of the pendulums exerted atthe power pivot of the pendulum lever I9 is greater than the downwardpull exerted by the Weight of the load receiver 3 and the leverssupporting it if the unbalance of the pendulum lever I 9 and the tarebeam lever 3 is eliminated. That is, the weighing scale is constructedso that the initial pull of the pendulum counterbalance exceeds theinitial pull of the platform lever system. To balance the scale aninitial pull, equal to the difference between the pendulum initial pulland the platform lever systeminitial pull, is provided by the unbalancedweights of the tare beam lever and the pendulum lever. The commonpractice has been to provide for this difference in initial pulls bychanging the amount of load in the loading box 52 of the tare beam lever8.

When this is done, and the vertical position or the loading box 52 isadjusted with respect to the tare beam lever B, the scale will indicatecorrectly throughout its weighing range as long as it is level but itcan be made to indicate correctly at only one point of the chart when itis tipped or out-oi-level.

According to the invention, the scale may be made to weigh and indicatecorrectly throughout its weighing capacity if the initial pull providedby the levers is divided betweenthem in the proper proportion. For mostcomplete compensation the initial pull from lever unbalance is dividedbetween the levers in amounts that are generally inversely proportionalto the arcs of travel of the weighing levers.

When a weighing scale is tipped, a condition to which portable scalesare subjected most of the time to a more or less degree, forces areintroduced into the weighing system that may or may not change thindication of load. A portable weighing scale is. normally adjusted toweigh and indicate correctly when it is'level. Its performance, when itis tipped or out-of-level, may be analyzed by considering that the forceof gravity acting on all the parts of the scale and the load is dividedinto two components'a't'right angles to each other, the first of which,a nearly vertical component, is parallel to the center line of thescale, while the other component, nearly horizontal, is perpendicular ortransverse to said center line of the scale. The magnitudes of thesecomponents are proportional to the cosine and the sine respectively ofthe angle through which the scale is tipped from a level position.Inasmuch as the indication of a level scale is the result of balancingthe forces of gravity acting on the load, the lever system, and thependulums, this balance of gravitational forces is not affected bytipping the scale because each of the forces is multiplied by the cosineof the angle of tip, thus varying their actual magnitude but not theircondition of balance.

The component of the gravity force acting transverse to the centerlinemay introduce changes in indication unless its effect on one part of theweighing mechanism is canceled by a counteracting effect on anotherportion of the system. The pendulums 26 are identical and rotate inopposite directions in counterbalancing load forces. The transverselyapplied component of gravitational force, however, tends to rotate thependulums in the same direction in equal amounts which tendenciescounteract and balance each other insofar as the indication of load isconcerned.

The levers of the scale, in particular the pendulum lever 19 and thetare beam lever 8 (schematically illustrated in Figures V and VI), aresubjected to the same transversely directed forces when the scale istipped. When the levers are in their no load position, the positionshown in Figure V, the power pivot end of each lever is above atransverse plane passed through its fulcrum. Figure V schematicallyillustrates the position of the tare beam lever 8 and the pendulum lever16, when the indicator of the scale stands at zero and the scale istipped to the left through an angle A. In the vector diagram,illustrating the lines of action of the forces, the vector O-Wrepresents the force of gravity applied to any part of the scale. Thevector O-Wv is the component of the gravity acting along a line parallelto the center line of the tipped scale. The vector O-WH is the componentof the force of gravity acting along a line perpendicular to the centerline of the scale. When the scale is level O-WH is zero and its effecton the lever system is zero.

When the scale is tipped the force represented by the vector O-WH actson the centers of gravity of each of the levers and exerts a momenttending to rotate the levers about their fulcrums, which moment isproportional to the weight of the lever and the moment arm of the force.The moment arm of the force is the distance, measured parallel to thecenter line of the scale, be-

tween the fulcrum of the lever and a line passed;

through the center of gravity of the lever perpendicular to the centerline of the scale. Thus, the force acts along the dotted line 59-60passed through the center of gravity (the point CG) of the pendulumlever l9 and above the fulcrum of the lever 19 so that the lever tendsto rotate counterclockwise. Also the force acting along a dotted line'61-62 that passes through the center of gravity of the tare beam leverand above its fulcrum tends to rotate the tare beam levercounterclockwise. The tare beam lever 8 and the pendulum lever l9 rotatein opposite directions when load 'is'applied to the scale. Therefore,the transversely directed force applied to the pendulum lever l9 tendsto drive the indicator toward zero, while the similarly directed forceapplied to the tare beam lever 8 tends to drive the indicator toward thefull scale end of the chart.

The centers of gravity for any chance distribution of the weight of thelevers may be located so that the effect of the transversely directedforce applied to one lever exactly cancels the transversely directedforce applied to the other lever for one arbitrarily selected positionof the levers. For example, the pendulum lever l9 may be assumed to havenegligible mass while the tare beam lever 8 has a comparatively largemass. If the center of gravity of the tare beam lever 8 is on its pivotline to the left of the fulcrum (Figure II) and the scale is tipped tothe left, the indicator oes fast at zero. If the center of gravity isdropped beneath the pivot line so as to be on a line that is parallel tothe line 6l62 and that passes through the fulcrum of the lever, themoment arm of the transverse force is zero and the zero indication ofthe scale is not affected by tipping the scale. As soon as load isapplied to the scale and the levers take up new positions, the linethrough the center of gravity of the tare beam lever 8 parallel to theline iii-62 no longer passes through the fulcrum but passes at somedistance beneath the fulcrum so that the transverse directed force tendsto rotate the tare beam lever clockwise, thereby causing the scale toindicate less load than is actually on the load receiver.

Figure VI illustrates the positions of the levers when the scale isloaded to capacity and is tipped to the left. The transverse forceacting on the centers of gravity on the levers tends to rotate thelevers clockwise. Clockwise rotation of the pendulum lever [6 causes thescale to indicate fast, while clockwise rotation of the tare beam lever8 causes the scale to indicate slow. The moments in the two leversresulting from the transversely directed force will cancel each other ifthe centers of gravity are properly located with respect to lines passedthrough the fulcrums of the levers. However, if the mass of the leversis not correct the positions of the centers of gravity to secure correctfull capacity indication in an out-of-level scale are not the same asthose for correct zero indication.

In order that the load indication throughout the weighing range shall beimmune to out-oflevel conditions of the scale, it is necessary that themoments produced in the levers by the transversely directed component ofgravity force shall cancel each other for all positions that the leversmay assume. The vertical travel of the center of gravity of the pendulumlever IS, the perpendicular distance between the position of the line 5968 of Figure V and the corresponding line 6364 of Figure VI, determinesthe change in moment produced in the pendulum lever by the transverseforce as the scale lever system moves through its weighing range.Likewise, the distance between the positions of the line 6l62 of FigureV and a corresponding line 65-66 of Figure VI represents the change invertical position of the center of gravity of the tare beam lever as thelevers move through their operating range. In order that the momentsproduced by the transverse force shall cancel each other throughout theentire operating range, it is necessary that the mass of one lever(assumed to be concentrated at its center of gravity) when multiplied bythe vertical travel of that center ofgravity times the angular travel ofthe lever shall be equal to the mass concentrated at the center ofgravity of the other lever when multiplied by the vertical travel ofthat center of gravity times the angular travel of the lever. 'As longas this relation holds it is immaterial whether the centers ofgravity beonthe pivot lines or whether they are displaced from the pivot lines byproportional amounts. When this relation holds the composite'center ofgravity of the levers moves along a straight line.

If the mass is proportioned between the levers to satisfy the statedproportionality but the centers of gravity are not properly positionedwith respect to the pivot lines of the levers the lever system willexhibit a change in initial pull when it is tipped but the change ininitial pull will be substantially independent of the leverpositions; 1. e. will be of the same magnitude throughout the weighingrange. Satisfactory operation is obtained if the centers of gravity areeach located on the pivot line of the respective levers or if they areboth displaced in the same direction either up or down through distancesthat are proportional to the vertical travel of the centers of gravity.In this condition of adjustment the composite center of gravity movesalong 'a straight line that is parallel to the center line of the scale.

Initial pull to secure a balance betw en the initial pulls of thependulums and the lever system may be provided by adding mass to theconnection between the levers. An example of a lever system that doesnot contribute an error when the scale is tipped, and in which theinitial pull may be adjusted by adding weight at asingle point, isillustrated in Figure VII; In this example, a tare beam lever 67 carriedon a fulcrum bracket 68 has a load pivot 69 towhich forces from a loadreceiver lever'system may be applied through a steelyard rod T0. A powerpivot ll of the tare beam lever 61 is connected through a stirrup andbearing 12 to the" lower end of a threaded steelyard rod 13 whoseuppere'nd is attached to a stirrup and bearing "suspended from a loadpivot 15 of a pendulum lever 76. The pendulum lever it has a fulcrumknife edge 11, resting on a bearing 1-8 whileits power pivot 19 isengaged bya stirru and bearing 8'0suspended from a pair ofloadcounterbalanclng pendulums or other automatic counterbalancingmechanism. A loading box Bl mounted on the steelya'rd rod 73 comprises acup-shaped body 82 having a drilled and tapped boss 83 formed in itsbottom surface andhaving a-removable cover '84;

If the loading-box-8 l is positioned at the lower end of the steelyardrod 73, its mass has substantially the sameeilect as'if weight wereadded at the power pivot ll of the tare beam lever. Therefore, whenthescale is tipped to the. left, the condition I described in connectionwith Figures V and VI, the scale tends to indicate fast at zero and slowat full load. Ifthe loading box BI is moved to the top end ofthe-steelyard rod 13 its mass may be considered concentrated at the loadpivot 'iE of the pendulum lever 76in which position it produces oppositeeffects when the scale is tipped. An intermediate position along alongthe steelyard rod i3 may be found at which the addition of weight to theloading box 8| does not-cause a'changein the scale indication whenthescale is tipped;

Since the initial pullof the scale maybe adjusted by adding weight tothe loading box 81, and since the distribution of that weight with.respect to the levers maybevariedby noving the loading box up and downalong the steelthe pendulum pull at the pendulum. Therefore, to effect ayard rod 73, it is possible to use the loading box to correct"differences in mass distribution between the levers so that the loadindications will not be affected by out or-level conditions of thescale. When the design of the scale housing limits the size of theloading box 8! and, therefore, the amount of mass that may be added atthat point the loading box -8l is used to supplement the initial pullprovided by unbalancing the pendulum lever and the tare beam lever.

As a matter of convenience and because of the weight of the poises- 47and 48, the loading boX for the tare beam lever is located on theopposite side of the fulcrum from its load and power pivots. Thisloading box is used to decrease the unbalanced mass of the tare beamlever to an amount such that the residual unbalance combined with theunbalanced pull of lev'er provides the desired initial change in massdistribution between the levers without changing the initial pull, it isnecessary to add toboth-orsubtract from both loading boxes. Kit isdesired to change the initial pull without changing the massdistribution, mass must be added to one and subtracted from the other.The advantage of the loading box 8| for securing final adjustments ofinitial pull is that mass may be added to the loading box and theaddition will not ailect the balance between the levers insofar asout-of-level weighing is concerned.

Ifmore than two levers are included in the force transmission leversystem, the levers may be grouped in pairs in which the levers from eachpair are fulcrumed on opposite sides of their common connection. Eachpair may then be balanced so thatit doesnot contribute an error when thescale is out-of-l'e'vel. If an odd number of levers greater than one isused and the levers are fulcrumed some on one side of the scale and someon the other, the odd lever, the one remaining after the others havebeen paired, maybe considered as divided into two component parts, onepart of which pairs with one of the other levers and the other part ofwhich pairswith another lever. Thus three levers may be considered astwo pairs in which one lever, insofar as out-of-level weighing isconcerned, balances the other two.

Various modifications of lever systems may be devised that satisfy therequirement that the resultant center of gravity of the unbalancedmasses moves-in a line parallel to the vertical center line of thescale.

v Having described the invention, I claim:

1. In a portable weighing scale, in-combination, a load counterbalancingmechanism, a platform supporting lever system, a force transmissionsystem between the platform lever system and the load counterbalancingmechanism, said-force transmissionsystem comprising two groups of leverseach containing at least onelever, one group which has its leversfulcrumed to one side of the common connections and the other group tothe other side, said levers being proportioned such that the sum of theproducts of the weight of each lever multiplied by the length of travelofits center of gravity multiplied by the angular travel of the leverfor one group is generally equal to the sum ofthe similar products forthe other group.

2. In a portable weighing scale, a pair of levers forming part *of afOI'CEItIflIlSIl'liSSlOh path, said le'vers'being arrangedto' rotate inopposite directions with changes in load and being proportioned so thatthe product of the weight times the travel of the center of gravitytimes the angular travel of one lever is generally equal to thecorresponding product of the other lever.

3. In a portable weighing scale, a pair of levers forming part of aforce transmission path, said levers being arranged to rotate inopposite directions with changes in load, said levers having theircenters of gravity located on their pivot lines remote from theirfulcrum axes and at distances from the fulcrum axes such that the weightof one lever times the vertical travel of its center of gravity timesits angular travel equals the corresponding product of the other lever.

4. In a portable weighing scale, levers forming part of a forcetransmission path from a load receiver supporting system to an automaticcounterbalance, a steelyard pivotally connected toand serving totransmit force between a pair of the levers that are fulcrumed atopposite sides of the steelyard, and a loading box mounted on thesteelyard with its center of gravity at a point that divides thesteelyard into segments that are 10 inversely proportional to thesegments of the levers included between the fulcrums and the connectionsto the steelyard.

5. A lever system according to the claim 4, in which the loading box isadjustably mounted on the steelyard so that its position may be selectedto compensate for variations in mass distribution of levers.

LAWRENCE S. WILLIAMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,279,835 Bousfield Sept. 24,1918 1,543,768 Hem June 30, 1925 2,208,555 Hurt July 16, 1940 2,294,819Williams Sept. 1, 1942 2,368,010 Eash Jan. 23, 1945 FOREIGN PATENTSNumber Country Date 516,172 Great Britain Dec. 27, 1939

